Tyre pressure

[Fisherman]

Apologies for bringing up a subject discussed many times on here.
I have mitchelin agilis tyres which I run at 65psi.
My van is a 3.5T ducato a class.
But once warmed up after a few miles they rise to around 72psi.
Reading some posts on here I may be running a bit under pressure.
Any opinions on this.

Thanks in advance.

 

[trevskoda]

I run my 6.3 ton bus at 65psi and tyres wear even, any harder and the edges wear and it is a hard ride on bumpy roads, but i have double wheel r axle, fronts fine at 65 to.

 

[RichardHelen262]

On our sprinter based motorhome rated 3850kg i run the rears at 65 and fronts at 55 psi

 

[Scotia]

I run the front at 65 and rear at 67 on a 5 ton double axle. When I came back from getting 4 new rear tyres fitted last month I found the mh was wandering on checking the pressure they had only put in 45psi.

 

[izwozral]

Was told by my mechanic and someone who had a tyre company, that one of the causes of tyres perishing is running them under inflated, as well as exposure to the sun.
Just to complicate matters, the tyre pressures should be adjusted according to load.

I've been running mine at 79psi as stipulated as I am always fully loaded.

 

[Scotia]

Was told by my mechanic and someone who had a tyre company, that one of the causes of tyres perishing is running them under inflated, as well as exposure to the sun.
Just to complicate matters, the tyre pressures should be adjusted according to load.

I've been running mine at 79psi as stipulated as I am always fully loaded.

Go on a diet then!

 

[maingate]

I run the front at 65 and rear at 67 on a 5 ton double axle. When I came back from getting 4 new rear tyres fitted last month I found the mh was wandering on checking the pressure they had only put in 45psi.

The rears seem a bit high to me. I had the old 747 with 5 Ton MAM and I ran them at 50 psi but on mine most of the weight was on the front axle (I had to be careful with the front axle loading).

My current van is on the same Alko chassis as yours and I run at 50 psi. Anything more and the rattles get louder. If your 2 rear axles are rated at 1500 Kg each and you are not overloaded then try dropping them a bit. You could also feed in your weight info on the Tyresafe website. They give figures properly for tag axle vans, anything with only 2 axles automatically give 80 psi for some reason.

 

[trevskoda]

My ex library bus is light loaded by miles, hence at 65psi rather than the 80/85 rated on the sidewall.

 

[colinm]

Apologies for bringing up a subject discussed many times on here.
I have mitchelin agilis tyres which I run at 65psi.
My van is a 3.5T ducato a class.
But once warmed up after a few miles they rise to around 72psi.
Reading some posts on here I may be running a bit under pressure.
Any opinions on this.

Thanks in advance.

Anyway to get back to OP.
All tyre pressures rise when used as they heat up, so that in itself is not a problem. What you need to consider is the size and load index compared to the axle loads, anything else is just random figures which are meaningless.

 

[Scotia]

The rears seem a bit high to me. I had the old 747 with 5 Ton MAM and I ran them at 50 psi but on mine most of the weight was on the front axle (I had to be careful with the front axle loading).

My current van is on the same Alko chassis as yours and I run at 50 psi. Anything more and the rattles get louder. If your 2 rear axles are rated at 1500 Kg each and you are not overloaded then try dropping them a bit. You could also feed in your weight info on the Tyresafe website. They give figures properly for tag axle vans, anything with only 2 axles automatically give 80 psi for some reason.

It us loud when hitting bumps, but looking at the tyre wear on the old tyres and it was even.

 

[mark61]

Yes, weigh bridge, axle weights, load index and do the calculations. Would be the best way. That doesn't mean knowing the temp increase is of no help though.

Those that go completely off piste with their choice of tyres have only two ways off working out a tyre pressure. The above and the temp increase after say 30 mins driving. You'll have to do a search because I can't remember exactly what it is, anyway it's surprisingly accurate.

I'll stick my neck out and guess if your pressure is going up over 10% cold to hot, your under inflated. Mainly cause I like sticking my neck out

 

[Fisherman]

I'll stick my neck out and guess if your pressure is going up over 10% cold to hot, your under inflated. Mainly cause I like sticking my neck out

Well being made from brass, your quite safe mark

 

[wildebus]

Yes, weigh bridge, axle weights, load index and do the calculations. Would be the best way. That doesn't mean knowing the temp increase is of no help though.

Those that go completely off piste with their choice of tyres have only two ways off working out a tyre pressure. The above and the temp increase after say 30 mins driving. You'll have to do a search because I can't remember exactly what it is, anyway it's surprisingly accurate.

I'll stick my neck out and guess if your pressure is going up over 10% cold to hot, your under inflated. Mainly cause I like sticking my neck out

It depends on the time of year for one thing.
I have found after using aftermarket TPMS systems for over 15 years on various vehicles the starting pressures vary significantly when "cold" - as "cold" in the UK can be anywhere from below -0C to over 25C, but the end "hot" temp if there is not a fault is consistant as the tyres get to an operating temp in around 20 minutes.
That is my take on the changing temps.
As far as 65 PSI goes, sounds about right to me for a 3.5t van.

 

[argoose]

Read a good article a while back and it mentioned the rule of 4&6.
Car tyres should rise 4psi cold to hot.
Van tyres should rise 6psi cold to hot.
Any more your under inflated.
Any less your over inflated.
Not gospel, but old mechanic thinking.
It struck a chord that tyres do increase, so why not quantify it. The values seem reasonable in my head, but also I feel the side walls after a run to check temp.

 

[Fisherman]

Read a good article a while back and it mentioned the rule of 4&6.
Car tyres should rise 4psi cold to hot.
Van tyres should rise 6psi cold to hot.
Any more your under inflated.
Any less your over inflated.
Not gospel, but old mechanic thinking.
It struck a chord that tyres do increase, so why not quantify it. The values seem reasonable in my head, but also I feel the side walls after a run to check temp.

Well that’s just about right, they normally rise from 65psi to 72-73psi.

 

[barge1914]

Same van as yours Bill, except a little heavier on the front axle with automatic and 140 engine.

I spoke to Michelin for confirmation of pressures as Roller Team recommend 80psi for both front and rear. Michelin we’re unrelenting in affirming 80psi on rear on all motorhomes with these tyres ‘for stability’. They did however say for my normal loaded axle weights 1800kg front and 1600kg back I could go down to 65 on the front for a more comfortable ride, with an absolute minimum of 55psi.

I had been running them like you at 65psi all round which gave a much more comfortable and adequately stable ride. At 80kg all round it was like driving on concrete wheels, bang bang rattle bang, and very poor traction soft ground.

I’ve since gone back up to 75kg on the back, staying at 65 on the front, but I’m not at all happy with the amount of noise that produces, or with having much harder tyres and what must be poorer grip on the lightly loaded and now more skittish rear. I had always understood it was better to have the better grip on the rears to avoid the back end ‘overtaking’ and skidding on wet roads when braking.

My previous van had also originally CP tyres, but Continental. That was heavy on the rear and light on the front. They were quite happy to recommend lower pressures more in keeping with the actual loading.

I can understand higher pressure on the more heavily loaded wheels to maintain tyre profile and avoid wear from too much tyre on the road. But still haven’t really had a satisfactory explanation of why it should be the converse on this van.

 

[mark61]

Well that’s just about right, they normally rise from 65psi to 72-73psi.

Much the same as the 10% then.

 

[Fisherman]

Much the same as the 10% then.

They only teach fractions up here

 

[wildebus]

Same van as yours Bill, except a little heavier on the front axle with automatic and 140 engine.

I spoke to Michelin for confirmation of pressures as Roller Team recommend 80psi for both front and rear. Michelin we’re unrelenting in affirming 80psi on rear on all motorhomes with these tyres ‘for stability’. They did however say for my normal loaded axle weights 1800kg front and 1600kg back I could go down to 65 on the front for a more comfortable ride, with an absolute minimum of 55psi.

I had been running them like you at 65psi all round which gave a much more comfortable and adequately stable ride. At 80kg all round it was like driving on concrete wheels, bang bang rattle bang, and very poor traction soft ground.

I’ve since gone back up to 75kg on the back, staying at 65 on the front, but I’m not at all happy with the amount of noise that produces, or with having much harder tyres and what must be poorer grip on the lightly loaded and now more skittish rear. I had always understood it was better to have the better grip on the rears to avoid the back end ‘overtaking’ and skidding on wet roads when braking.

My previous van had also originally CP tyres, but Continental. That was heavy on the rear and light on the front. They were quite happy to recommend lower pressures more in keeping with the actual loading.

I can understand higher pressure on the more heavily loaded wheels to maintain tyre profile and avoid wear from too much tyre on the road. But still haven’t really had a satisfactory explanation of why it should be the converse on this van.

When you say "these tyres", which tyres are you referring to?
It is well known that michelin go on about 80PSI on the Aglis Camping Tyres, but what about the other Aglis tyres (as far as I know, "Aglis" is their term for van tyres - be they camping or any other type. I have Michelin 'Aglis' tyres on my Motorhome but they are not Camping ones)

 

[trevskoda]

I put anything on if cheap, just bought 5 of ebay with over 9mm tread, got them this morning and they are like new, and at a fraction of what tyre shops wanted here, 3 are winter mud and snow.